This fixes the problem that dccp_probe output can grow quite large without
apparent benefit (many identical data points), creating huge files (up to
over one Gigabyte for a few minutes' test run) which are very hard to
post-process (in one instance it got so bad that gnuplot ate up all memory
plus swap).
The cause for the problem is that the kprobe is inserted into dccp_sendmsg,
which can be called in a polling-mode (whenever the TX queue is full due to
congestion-control issues, EAGAIN is returned). This creates many very
similar data points, i.e. the increase of processing time does not increase
the quality/information of the probe output.
The fix is to attach the probe to a different function -- write_xmit was
chosen since it gets called continually (both via userspace and timer);
an input-path function would stop sampling as soon as the other end stops
sending feedback.
For comparison the output file sizes for the same 20 second test
run over a lossy link:
* before / without patch: 118 Megabytes
* after / with patch: 1.2 Megabytes
and there was much less noise in the output.
To allow backward compatibility with scripts that people use, the now-unused
`size' field in the output has been replaced with the CCID identifier. This
also serves for future compatibility - support for CCID2 is work in progress
(depends on the still unfinished SRTT/RTTVAR updates).
While at it, the update to ktime_t was also performed.
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
---
net/dccp/probe.c | 68 ++++++++++++++++++-----------------------------------
1 files changed, 23 insertions(+), 45 deletions(-)
--- a/net/dccp/probe.c
+++ b/net/dccp/probe.c
@@ -46,77 +46,55 @@ struct {
struct kfifo *fifo;
spinlock_t lock;
wait_queue_head_t wait;
- struct timeval tstart;
+ ktime_t start;
} dccpw;
-static void printl(const char *fmt, ...)
-{
- va_list args;
- int len;
- struct timeval now;
- char tbuf[256];
-
- va_start(args, fmt);
- do_gettimeofday(&now);
-
- now.tv_sec -= dccpw.tstart.tv_sec;
- now.tv_usec -= dccpw.tstart.tv_usec;
- if (now.tv_usec < 0) {
- --now.tv_sec;
- now.tv_usec += 1000000;
- }
-
- len = sprintf(tbuf, "%lu.%06lu ",
- (unsigned long) now.tv_sec,
- (unsigned long) now.tv_usec);
- len += vscnprintf(tbuf+len, sizeof(tbuf)-len, fmt, args);
- va_end(args);
-
- kfifo_put(dccpw.fifo, tbuf, len);
- wake_up(&dccpw.wait);
-}
-
-static int jdccp_sendmsg(struct kiocb *iocb, struct sock *sk,
- struct msghdr *msg, size_t size)
+static void jdccp_write_xmit(struct sock *sk)
{
const struct inet_sock *inet = inet_sk(sk);
struct ccid3_hc_tx_sock *hctx = NULL;
+ struct timespec tv;
+ char tbuf[256];
+ int len, ccid = ccid_get_current_id(dccp_sk(sk), false);
- if (ccid_get_current_id(dccp_sk(sk), false) == DCCPC_CCID3)
+ if (ccid == DCCPC_CCID3)
hctx = ccid3_hc_tx_sk(sk);
- if (port == 0 || ntohs(inet->dport) == port ||
- ntohs(inet->sport) == port) {
- if (hctx)
- printl("%d.%d.%d.%d:%u %d.%d.%d.%d:%u %d %d %d %d %u "
- "%llu %llu %d\n",
+ if (!port || ntohs(inet->dport) == port || ntohs(inet->sport) == port) {
+
+ tv = ktime_to_timespec(ktime_sub(ktime_get(), dccpw.start));
+ len = sprintf(tbuf, "%lu.%09lu %d.%d.%d.%d:%u %d.%d.%d.%d:%u %d",
+ (unsigned long) tv.tv_sec,
+ (unsigned long) tv.tv_nsec,
NIPQUAD(inet->saddr), ntohs(inet->sport),
- NIPQUAD(inet->daddr), ntohs(inet->dport), size,
+ NIPQUAD(inet->daddr), ntohs(inet->dport), ccid);
+
+ if (hctx)
+ len += sprintf(tbuf + len, " %d %d %d %u %llu %llu %d",
hctx->ccid3hctx_s, hctx->ccid3hctx_rtt,
hctx->ccid3hctx_p, hctx->ccid3hctx_x_calc,
hctx->ccid3hctx_x_recv >> 6,
hctx->ccid3hctx_x >> 6, hctx->ccid3hctx_t_ipi);
- else
- printl("%d.%d.%d.%d:%u %d.%d.%d.%d:%u %d\n",
- NIPQUAD(inet->saddr), ntohs(inet->sport),
- NIPQUAD(inet->daddr), ntohs(inet->dport), size);
+
+ len += sprintf(tbuf + len, "\n");
+ kfifo_put(dccpw.fifo, tbuf, len);
+ wake_up(&dccpw.wait);
}
jprobe_return();
- return 0;
}
static struct jprobe dccp_send_probe = {
.kp = {
- .symbol_name = "dccp_sendmsg",
+ .symbol_name = "dccp_write_xmit",
},
- .entry = jdccp_sendmsg,
+ .entry = jdccp_write_xmit,
};
static int dccpprobe_open(struct inode *inode, struct file *file)
{
kfifo_reset(dccpw.fifo);
- do_gettimeofday(&dccpw.tstart);
+ dccpw.start = ktime_get();
return 0;
}
-
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